Despite being pretty far north of the border, we have lots of options for Mexican food. But Qdoba Mexican Grill distinguishes itself by giving diners almost full control of the menu.

But the free-flowing system can be a double-edged sword–expansive possibilities mean you have the freedom to tailor a perfectly nourishing lunch, but it can also be overwhelming to have so many choices at your fingertips (especially when they aren’t all good for you).

We enlisted Cristin Wipfler, MPH RD, to analyze the mammoth menu and come up with some healthy choices–and some to avoid like the cheese-covered plague.

A few rules of thumb for Qdoba, according to our expert: The salsas are basically interchangeable, the seasoned ground meat is not your friend (one serving has 240 calories and 16 grams of fat), and guacamole, while filled with healthy fats, should still be enjoyed in moderation.

Since there are so many ways to customize dishes at Qdoba, Wipfler picked the popular choices to break down: burritos, tortilla bowls, and “craft 2” burritos.

• Best built: Start with a plain burrito with no dressing. Skip the tortilla and try a naked burrito with black beans, pico de gallo, cilantro-lime rice, lettuce, grilled veggies, and ranchera sauce–it’s 460 calories, 7 grams of fat, and 1,220 milligrams of sodium, and the 18 grams of protein and 20 grams of fiber will keep you full.

TACO BOWLS

“The kicker here is that the crunchy tortilla shell bowl is 390 calories and 22 grams of fat–just the bowl,” Wipfler warns. “My recommendation with this is to break off piece of the bowl and crumble it over your salad to enjoy the crunch. Just don’t eat the whole bowl.”

Following Wipfler’s tip automatically cuts calories and fat and shaves about 100 milligrams of sodium from the meal.

• Worst built: Pairing the nachos and the grilled quesadilla is one of the worst meals you can eat at Qdoba. The three-cheese queso over handmade tortilla chips plus the ‘dilla (shredded cheese between flour tortillas) are worth 645 calories and 36 grams of fat–and you haven’t even added anything yet! Wipfler says, “This craft 2 should come with a side of cardiologist.”

• Best built: “The best combo I could find is the naked taco salad with chicken and grilled veggies, paired with the tortilla soup,” our expert says, adding that there’s even room to throw in sour cream and tortilla chips. This craft 2 pick is a reasonable 325 calories, 15 grams of fat, and 1,355 milligrams of sodium.

You may have noticed that most of the combinations yield inordinate sodium levels–which is an unfortunate commonality for quick-service restaurants.

“I tell my clients to split–share with a friend or automatically ask for half in a doggie bag when you order. If you eat half, you’re getting half the sodium,” Wipfler recommends.

To stay on the healthy side of any menu, pile on the veggies, exercise some portion control, be careful with the extra toppings, and flex your substitution power.

“The biggest thing to remember when you’re walking in is that you can ask for anything–the worst they can do is say no,” Wipfler says. “You should be able to get smaller serving sizes, or substitute beans for meat. Don’t be afraid to ask for what you want to make your meal healthier.”